Cores



June 25, 1957 w.oG1 EsBEE ETAL 2,797,395

comas Filed Jan. 22, 1952 2 Sheets-Sheet l INVENTORS Wendell Oglesbee 8\ Archie R. Cornell.

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ATTORN EY June 25, 1957 w. oGLEsBEE ETAL 2,797,395

INVENTORS Wendell Oglesbee 8 Archie R. Cornell.

mm 7m ATTORNEY AWITNESSES: 8

CRES

Wendell Uglesbee, Lakewood, and Archie R. Cornell, Avon Lake, Ghio, assignors to Westinghouse E ieetrac Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application anuary 22, 1952, Serial No. 267,628 6 Claims. (Cl. 336-165) This invention relates generally to magnetic core constructions, and more particularly to core constructions for stationary inductive apparatus.

In certain types of magnetic cores, such as the cores for the transformer and ballast coils employed for controlling operation of electric gaseous discharge devices, it is necessary to introduce leakage paths between certain of the coils, or provide varying reactance of the coils, and in some cases to vary the reluctance of the magnetic circuits of the several coils. This has been done inthe past by providing gaps in the core structure at des1red points, but ditliculties have been encountered due to the rather critical nature of such gaps and the difficulty in economically and accurately stamping out laminat'ions, stacking and securing 'them together while maintaining gap accuracy. n

Accordingly, one object of this invention is to provide a novel core construction having one or more gaps therein, which is economical to construct while maintaining accurate gap dimensions and permitting easy adjustment during assembly. I

Another object of this invention is to provide a core construction rhaving one or more gaps therein provided in a novel manner between at least two core stampings which are in engagement -at least at two spaced lpoints.

Another objectof this invention is to provide a core construction having one or more Vgaps Vformed 'therein between apair of core stampings and-arranged in a novel manner permitting adjustment of the gaps simply by relative longitudinal mov-ement of the'core stampings.

Another object of this invention is to provide a novel laminated core construction wherein `each lamination comprises a .plurality of .parts shaped in a manner to provide a core construction of the type described when assembled, and-yet capable of being stamped out of a single sheet Vof magnetic material with -a minimum 4of waste.

vThese and other objects of this invention will become more apparent upon consideration ofthe following detailed description of preferred embodiments thereof, when taken infconnection withlthe attached drawings-in which:

Figure `1 is aplanviewof a core construction assembled in accordance with this invention; i

Fig. 2 is a viewlike Fig. `il of a modified core` construction;

Fig. 3 is a v-iewlikeFigs. l and 2 of still another modiiied form of the invention;

2,797,395 Patented June 25, 1957 adapted to be employed with transformer and ballast coils to form a unitary transformer and ballast assembly for the control of gaseous electric discharge devices, such as fluorescent lamps, for example in the manner specifically described and claimed in our copending application, Serial No. 267,627, on Apparatus For Operating G'aseous Discharge Devices, tiled January 22, 1952, and assigned to the same assignee of this invention.

The particular core 2 shown in Fig. l is also disclosed in our above-identified copending application, but is not claimed therein per se. The core 2, as are all the cores herein disclosed, is built up of a stack of laminations formed from a suitable magnetic material, such as a good magnetic steel, with each lamination comprising two or more parts of a particular configuration which may readily be punched out from a strip of magnetic material and assembled to form the core itself, The core 2 comprises a winding leg 4, which is of rectangular form having straight, parallel side edges, and straight, parallel end edges extending at an angle of substantially to the side edges. Each lamination also includes a pair of identically formed substantially L-shaped yoke members 6, each of which includes a long leg 8, which extends along one side of winding leg 4 in spaced relation thereto and a short leg 10, which extends downwardly across one end of the winding leg 4 in spaced relation thereto. Each yoke member 6 is also provided with a pair of spaced laterally extending shorter legs 12, one of which is located at the opposite end of the yoke member from the leg 10, and the other of which is located adjacent to leg 16, but spaced a substantial distance from it. Each yoke member 8 also has a fourth leg 14, which is wider than the legs 1t) and 12, but is shorter than legs 12. All of the yoke legs 10, 12 and 14 extend laterally from the long leg 8 in the same direction.

In assembling each lamination of core 2, the yoke members 6 are positioned at opposite sides of the winding leg 4, with the legs 10, 12, and 14 facing each other, and with end legs 12 of the yoke members aligned with one end of the winding leg 4 (the left hand end as viewed in Fig. 1). The legs 12 of the yoke members 6 when in engagement with the adjacent side edge of the winding leg 4, act to provide a gap of predetermined spacing between leg 14 of each yoke member and the adjacent side edge of the winding leg 4. There may also be a space between the two legs 10 of the yoke members 6 at the opposite end of the winding leg 4 (the right hand end as viewed `in Fig. l) to insure proper engagement of legs 12 and winding leg 4. Moreover, since the winding leg 4 has straight side edges, the gap between the right hand end of the winding leg 4 and the legs 10 of the yoke members 6 may be readily adjusted merely by longitudinally moving the winding leg 4, `and may be readily made to be any predetermined amount by the use of a spacer of the desired thickness (not shown) of any suitable nonmagnetic material, such as an insulating paper.

As previously mentioned, the core construction shown in Fig. l as well as those to be hereinafter specifically described, are designed to employ the coil arrangements of the above-mentioned copending application, one of which is schematically shown in Fig. 4 to comprise an auto-transformer coil 102, having a primary portion 104 connected by conductors 1% and 103 to a suitable low voltage source of supply. The secondary portion of the auto-transformer coil `is connected at its free end to a lead ballast coil 112 which, in the circuit disclosed inthe above-mentioned copending application, is adapted to be connected in series with a condenser to one terminal of yone lamp, the other terminal of which is connected to lone of the supply conductors, for example, the conductor 106. There is also `a lag ballast coil 11S which is connected from a tap 116 on the transformer coil, for example herein illustrated as being at the juncture of the primary and secondary parts of auto-transformer coil 102, to a conductor 120 which is connected to one terminal of a second fluorescent lamp, the other terminal of which is also connected to supply conductor 106. As explained in our above-mentioned copending application, the tap 116 may be located at any desired point on the transformer winding102. The coils tare adapted to be assembled with the cores herein disclosed in substantially the same manner more particularly described and claimed in the abovementioned copending application.

Generally, the auto-transformer coil 102 is mounted in the center opening `of core 2 between the yoke legs 12 at the right (Fig. l) and legs 14, and the lag ballast coil 118 is mounted in the opening formed between end lyoke legs 12 and legs 14, although, as pointed out in our abovementioned copending application, the location of autotransformer coil 102 and lag ballast coil 118 may be interchanged if desired to obtain a somewhat different heat distribution in the core. The lead ballast coil 112 is mounted in the remaining opening of the core, that is, the opening between yoke legs :and adjacent legs 12 at the right hand end of the core, as viewed in Fig. l.

It will thus be apparent that the core 2 provides a closed magnetic circuit which extends through the portions of the winding leg 4 and the yoke members 6 located between yoke legs 12 and through these legs, so that the lag coil 118 acts as an extended secondary for the primary portion 104 of the auto-transformer coil, while at the same time has a relatively high reactance due to the leakage gap provided between lag coil 118 and the auto-transformer coil 102 between yoke legs 14 and the winding leg 4. On the other hand, lead coil 112 is located outside of the magnetic circuit through the core for the auto-transformer coil, but its magnetic circuit comprises a part (adjacent legs 12) of the magnetic circuit through the core for the autotransformer coil 102. This results, as fully explained in the above-mentioned copending application, in the application of a relatively high voltage across the lamp connected between conductors 106 and 114, it being the voltage across the entire auto-transformer coil plus whatever voltage may be induced in the loosely coupled lead coil 112, and a voltage of substantially the same value may be applied across the other lamp, with it being the voltage across the primary portion 104 of the auto-transformer coil in this instance, and lag coil 118. At the same time both lamps are adequately ballasted due to the high reactance of coils 112 and 118. Coil 118 is termed a lag coil due to the inductive nature of its circuit, whereas coil 112 is termed a lead coil because a suitable condenser is connected in series in its circuit to provide a leading current, and thus provide a high overall power factor, :and correct for the stroboscopic effect of the two lamps.

Due to the fact that core 2 is constructed so that several coils are adapted to be mounted thereon and employ the same, or parts of the same magnetic circuit, it will be appreciated that considerable savings are achieved in the weight land size of the core, thus making it considerably more economical to manufacture than previous constructions. Further savings are realized in the assembly operation, because it is merely necessary to assemble yoke members 6 with the legs 12 thereof in engagement with opposite sides of the winding leg 4, and this automatically establishes the desired leakage gap between yoke legs 14 and the winding leg 4, as well as clearance between yoke legs 10. The gap between yoke legs 10 and the adjacent end of the winding leg 4 may then be easily adjusted by longitudinal movement of the winding leg 4 itself. In addition, the specific conguration of the parts of each lamination effect a considerable saving in waste material during the stamping out of these parts because the yoke members 6 may be interleaved during stamping, and of course, the winding leg 4 can be stamped out with substantially no waste whatsoever due to its regular formation. A further advantage of this construction is that it permits the center leg to be made of oriented grain magnetic steel, with the grain ptarallel to the long dimension of the winding leg 4, as such a material can be used to best advantage with the flux path being parallel to the grain, and since such a material has a high permeability, it results in a further reduction in the size of the core.

The modified form of core 22, shown in Fig. 2 of the drawings, uses a yoke member 24, which is generally rectangular in form and is stamped in one integral piece, and is adapted for use with a central winding leg 26. The yoke member 24 has sides 28 integrally joined to an end leg 30 at one end, and an end leg 32 at the other endl thereof. The end leg 30 of the yoke member 28 has a. rounded recess 34 formed at a central point at the inner side thereof for receiving the complementary shaped end' of the winding leg 26. Rounded recesses 38 are formedv at opposite sides of the winding leg 26 adjacent the opposite end thereof for receiving the rounded ends of yoke legs 40 which are extended laterally from the sides- 28 of the yoke 24, into engagement with the winding leg. 26. The winding leg 26 has relatively short legs 42 extended in opposite directions therefrom toward the relatively short legs 44 extending from the sides 28 of the yoke 24 to form a magnetic leakage gap between the legs 42 and 44. If desired, the magnetic leakage gap may be formed as in Fig. l by making legs 44 longer and having winding leg 26 formed with straight sides, or notched as in Fig. 7, depending on the length of legs 44.

It will be observed that the magnetic circuit through the core 22 is similar to that through the core 2 shown in Fig. 1, with the principal difference between these two cores being that the yoke 24 is formed of integral one piece construction so that it may be stamped out in a single operation. Otherwise, the size of core 22 and its weight and cost are comparable to the core 2 shown in Fig. l, due to the similarity in the magnetic circuits through the core.

The core 46 shown in Fig. 3 of the drawings is similar to the core 22 shown in Fig. 2 in that it has a one piece rectangular yoke member 48, having opposed parallel sides 50 integrally formed with end legs 52 and 54. The end leg 54 is provided with an angularly shaped recess 58 at its inner side for receiving a complementary shaped end of a centrally located winding leg 56. The opposite end of the winding leg 56 is spaced from the leg 52 of the yoke member to form a gap 60, similar to the gap 36 in the core 22 shown in Fig. 2. Rectangular recesses 62 are formed in the winding leg 56 at opposite sides thereof, for receiving the inner ends of legs 64 which extend toward each other from the sidesv 50 of the yoke member 48. In this embodiment of the invention, the winding leg 56 is also formed with oppositely extending legs 66 which terminate short of the sides 50 of the yoke member 48 to form a magnetic leakage gap at these points.

The core 46 shown in Fig. 3 is essentially similar to that shown in Fig. 2 except that the inter-fitting recesses are angularly shaped rather than being rounded as in Fig. 2, and the leakage gap at an intermediate part of the winding leg is formed by legs projecting from the winding leg 56, whereas in the core 22 shown in Fig. 2, this gap is formed in part by legs integral with the winding leg 26, and in part by legs 44 integral with sides 28 of the yoke member 24.

The core 68 shown in Fig. 5 of the drawings is very similar to the core shown in Fig. l, having identical yoke members, and, accordingly, such identical members and parts thereof are identied with the same reference numerals, and a detailed description thereof will not be repeated. The core 68 of Fig. 5 differs from that shown in Fig. 1 in that the winding leg 70 is provided with a step 72 on one side thereof at one end, and there may also be provided an identification notch 74 adjacent the step 72, to facilitate assembly.

With the step 72 ofthe winding leg 70 located atthe left hand `end'of core v 68,as lis shown in Fig. 5, the shunt gap betweenyoke leg 14 adjacent step 72 and the winding leg 70 may be'made to be less than the gap between these legs and winding leg A4 of the core 2, shown in Fig. 1, during-assembly ofthe yoke members'and'the winding leg. Thus, in order for both legs 12 of theupper yoke member 6 (FigpS) to engage the adjacent side of windingy leg 70, it is necessary that a relative tilting action take place about the corner ofthe inner leg 12 adjacent the leg 14. Only the left-hand corners of legs 12 will then engage thewinding leg 70.

The core 76 shown in Fig. 6 of the drawings is formed of parts which are identical with the 'parts of core 68 shown in Fig. 5, and accordingly such parts are identified by the same reference numerals and a detailed description thereof will not be repeated. The only difference between the core 76 shown in Fig. 6 and the core 68 shown in Fig. 5 is that the windingl leg 70 is turned end for end so that the step 72 is located at the right hand end of the core as viewediin Fig. 6. This meansthat the width of the gap between the winding leg'70 and yoke leg 14 at the top, as-viewed lin the drawings,'is greater in the core 76 shown in Fig. 6 than it is for the core 68 shown in Fig. 5.

The core 78 shown in Fig. 7 of the drawings is also quite similar to the cores 2, 68 and 76 shown in Figs. 1, 5 and 6 respectively, but differs from these previously described-cores by having both the winding leg and yoke members somewhat modified. Thus, the winding leg'8tl,

while being of rectangular form, has opposed shallow i notches 82 formed therein at a point opposite opposed inwardly extending yoke legs 94 integral with the sides 86 of identical L-shaped yoke members 84.

In addition, the long side legs 86 of each yoke member 84, each have a short leg 88 which is positioned adjacent to, but spaced from the right hand end of the winding leg 80 as viewed in'Fig. 7, with the legs 88 also being spaced from `each other. Each of the yoke members 84 has a leg 92 at the end thereof opposite leg 88, and a leg 98 intermediatelegs'SS and 94, with all three legs 90, 92 and 94 of each yoke member beingof the same length.

yIt will be-observed that the core 78 has substantially the same low reluctance magnetic paths and leakage` gaps as the cores previously described, with its distinguishing characteristic being that theleakage gap between legs 94 and the winding leg80 is formed and determined by the depth of notches 82 formed in the winding leg 88. This somewhat simplies the structure of theyoke members 84, inasmuchas the three legs 90,92 and 94 are identical in frlength, withrlegs 90 and 92 in engagement with'the windi ing leg 80, to thus predetermine the length of leakage gaps between yoke legs 94 and the winding leg 80, as well as the gap between yoke legs 88.

It will be understood that all of the cores described above are formed by stacking a number of the laminations shown, in the manner shown in Fig. 8, and the laminations may then be secured together in any desired manner such for example as by clamping or welding. In this regard, certain of the core constructions disclosed herein lend themselves particularly well to a welded construction. Thus, for example, the core constructions shown in Figs. 1, 5 and 6 may be secured together by Welding at the points 16 and 18 which form the junctures at one end between the yoke member 6 and the winding leg 4, and at the point 20 where the gap is located between yoke legs 10. Similarly, the core of Fig. 7 may be welded at corresponding points 96, 98, and 100. The cores shown in Figs. 2 and 3 may also be welded or otherwise secured.

It will be noted that all of the core structures shown in Figs. 1 to 3 and 5 to 8 have certain features in cornmon, with the principal feature being that the yoke member or members have portions which are in engagement with the winding leg over a substantial area at two spaced points so as to facilitate assembly of the core into a stack of laminations and final welding or otherwise securing the 'stacked :laminations together. lThis two kpoint engagement of thewinding leg and yoke member or members provides predetermined leakage gaps in each of the core constructions with the length of all Yof the 'gaps being predetermined in the cores shown in Figs. 2 and 3, as well as all of rthe gaps in the remaining cores, except for the one at'the right hand end of the winding leg which may be readily adjusted to compensate for any manufacturing differences in the capacitor which may be used in circuit with the lead coil 112 by simply longitudinally moving the winding leg itself. In the core designs shown in'Figs. 5 and 6 an additional adjustment may be effected by reason of the stepped construction of the winding leg as previously explained.

Having described preferred embodiments of the invention in accordance with the patent statutes, it is desired to point out that the invention is not limited to the rspecific form and detail of these illustrative embodiments,

inasmuch as it will be apparent to persons skilled in the art that various changes and modications may be made whileretaining'the essential features of the invention. Accordingly, it is desired that the invention may be interpreted asl broadly as possible in view of the prior art.

We claim as our invention:

l. A coreconstruction comprising, an elongated winding leg having a straight side, an L-sh'aped yoke having the short Vleg thereofpositioned adjacent to but spaced from one end of said winding leg and the long leg thereof extending parallel to said winding leg and terminating at the other end'of said winding leg, said long leg having a pair of spaced relatively short legs of the same length extending laterally from said long leg into engagement with the straight side of said winding leg, a shorter leg extending laterally from said long leg toward said winding leg at a location spaced from both of said pair of short legs, said winding leg having a notch in said straight side at least as long as the width of one of said pair of short legs, and said notch being located so that'it may be selectively locatedin opposition to said one of said pair 'of short legs or not when the free Aend of the long leg of the yoke'is substantially aligned with the other end of said winding leg by turning said winding leg end for end.

2. A laminated core construction comprising a stack of laminations of magnetic material with each lamination including an elongated winding leg having opposed straightisides, a pair of separate identical L-shaped yoke members `positioned at opposite sides of said winding leg with the `short legsr of'said'yoke members positioned adjacent to `but longitudinallyspaced outwardly from one end of said winding leg and from each other, the long leg of each yoke member terminating at its opposite end at the other end of said winding leg, each yoke member having a pair of spaced relatively short legs of the same length extending laterally therefrom into engagement with the adjacent side of said winding leg and being of less length than said short legs of the yoke members to maintain the aforesaid short legs of the yoke members in spaced relation to each other a distance less than the width of said winding leg member, and said laminations being secured by welding at the gap between the short legs of said yoke members and at the point of engagement of one of said pair of legs of each yoke member and said winding leg.

3. A core construction comprising, an elongated winding leg member, an elongated yoke member extending along one side of said winding leg member in spaced relation thereto, but having spaced legs extending into engagement with the adjacent side of said winding leg member at spaced points therealong, means on at least one of said members at a third spaced point, extending into proximity to but being spaced from the other of said members to form a leakage gap, said winding leg having a recess in one side at least as long as one of said spaced legs, and said notch being located so that it may 7 be selectively located in opposition to said one spaced leg or not by turning said winding leg end for end and substantially aligning the ends of said yoke member and winding leg.

4. A core construction comprising, an elongated winding leg member, a pair of separate elongated yoke members extending along opposite sides of said winding leg member in spaced relation thereto but each having spaced legs extending into engagement with the adjacent side of said winding leg member at spaced points therealong, means on at least one of said members at a third spaced point extending into proximity to but being spaced from the other of said members to form a leakage gap, and another leg on each of said yoke members which are longer than said spaced legs and extend towards each other at a point longitudinally spaced outwardly from one end of said winding leg member with the outer ends of said other legs being spaced apart a distance less than the width of said winding leg member and located in overlapping relation to said one end of the winding leg member at a location adjacent to but spaced longitudinally outwardly from said one end of said winding leg member to form another gap between said one end of the winding leg member and the adjacent sides of said other legs which is adjustable by relative longitudinal movement of said members with the spaced legs in engagement with said winding leg member and said spaced legs comprising the sole support of each yoke member on said winding leg member during assembly of said core construction, and means for securing said members together to maintain them in adjusted position with the spaced legs of each yoke member independently engaging said winding leg member.

5. A core construction formed to provide three winding openings comprising, an elongated winding leg member, a pair of separate elongated yoke members extending along opposite sides of said winding leg member in spaced relation thereto, but each having spaced legs extending into engagement with the adjacent side of said winding leg member at one end and at an intermediate point adjacent to but spaced from the other end thereof, means on at least one of said members at a third spaced point intermediate said spaced legs extending into proximity to but being spaced from the other of said members to form a leakage gap, and another leg on each of said yoke members at said other end thereof which extend towards each other to a point opposite but spaced longitudinally outwardly of said other end of said windsaid spaced legs so as to overlap the adjacent end of said winding leg member to form aY second gap betweenthe inner sides of said other legs and the adjacent end of said vwinding leg member which can be adjusted by relative longitudinal movement of said members, while the space between said other legs permits the aforesaid adjustment while said spaced legs engage their respective sides of the winding leg; f Y

6. A core construction comprising, an elongated-winding leg member, a pair of separate elongated yoke members extending along opposite sides of said winding leg member in spaced relation thereto but each having spaced legs extending into engagement with the adjacent side of said winding leg member at spaced points therealong, means on at least one of said members at a third spaced point extending into proximity to but being spaced from the other of said members to form a leakage gap, and another leg on each of said yoke members 'which are longer than said spaced legs and extend towards each other at a point longitudinally spaced outwardly from one end of said winding leg member with the outer ends of said other legs being spaced apart a distance less'than the width of said winding leg member and located in overlapping relation to said one end of the winding leg member at a point in opposition to but spaced longitudinally outwardly from said one end of said winding leg member to form another gap between said one end of the winding leg member and the adjacent sides of said other legs of said yoke members which is adjustable by relative longitudinal movement of said members, while the space between said other legs permits the aforesaid adjustment while said spaced legs engage their respective sides of the winding leg.

References Cited in the le of this patent UNITED STATES PATENTS 1,841,685 Sola .Jan. 19, 1932 1,893,251 Sola Ian. 3, 1933 2,393,439 White et al Ian. 22, 1946 2,429,604 Boucher Oct.y 28, 1947 2,553,554 Dierstein May 22, 1951 2,553,591 Kronmiller May 22, 1951 2,558,293 Feinberg June 26, 1951 2,562,693` Brooks July 31, 1951 2,577,733 Bridges Dec. 11, 1951 2,646,552 Shingledecker etal July 21, 1953 FOREIGN PATENTS 395,441 Great Britain July 20, 1933 439,964 Great Britain Dec. 18, 1935 544,997 Great Britain May 6, 1942 

